This laboratory is focused on calciotropic hormones in reproduction and development, with special emphasis on the uteroplacental units of mice and humans. This proposal is focused on parathyroid hormone-related protein (PTRrP), a hormone that inhibits uterine contractions (in rats), increases placental calcium transport (in sheep), and relaxes vascular smooth muscles in a variety of systems. The present studies continue work which identified abundant expression of PTHrP in human amnion and documented its decrease following rupture of the amniotic sac. Central hypotheses of the studies are (1) that PTHrP expression in human amnion is increased by mechanical signal transduction ("stretch"), is decreased by loss of stretch (e.g., as occurs after rupture of the amniotic sac), and is regulated by key hormones and growth factors of the uteroplacental unit, and (2) that uterus and placental blood vessels are target tissues for PTHrP in the human uteroplacental unit. The specific aims are: (1). To identify the mechanisms that control PTHRP expression in human amnion. This will be accomplished by in vitro studies of amnion cells (a) subjected to stretch, (b) treated with hormones (e.g., 1,25(OH)2 vitamin D) and growth factors (e.g., EGF) of the uteroplacental unit, and (c) treated with probes (e.g. phorbol esters, forskolin, calcium ionophore) of the likely signal-transduction pathways. (2) To identify candidate target tissues for PTHrP in the human uteroplacental unit. This will be accomplished by studies of binding of PTHrP, PTH and hormone fragments and characterization of PTH/PTHrP receptor mRNA in these tissues. (3) To define the cellular and subcellular localization of PTHrP and PTHrP mRNA within the (multi-layered) human amnion. This will be accomplished by light and electron microscopic immunochemical studies with antibodies directed against key regions of the PTHrP molecule. Because PTHrP relaxes uterine and vascular smooth muscle, these studies have potential importance for understanding mechanisms that produce premature uterine contractions (and thus, premature birth) and intrauterine growth retardation associated with impaired placental blood flow.